My '55 car has a manual pump under the dash , you push-pull the grey plastic knob until water squirts from the jets.
When I got the car the ( plastic) wash bottle was empty , I put some water in and pumped away and it worked !
some months later , having put proper wash solution in , would not work ,just some faint bubbling at the jets.
looked under the dash , shone torch on the clear plastic flexible tubing system , could see a lot of blackish particles , bit like soot , in all the flexibles , plus a lot of bubbles , and foaming a bit like a beer pour .
removed all the tubing , removed the pump , tried pumping water through. On the delivery stroke more black particles being pushed out the tubes connected to pump , both inlet and outlet . Also noted a bit of air bubbling out from where back lid fits on cylindrical casing . Assume that on suction stroke air is being pulled in through same place hence the two-phase 'beer pour' foam being delivered.
Have run some silicone sealant round the joint to see if that helps .
Question - is anyone familiar with the internals of these ( 60 year old ) pumps , should there be non return valve on inlet side to stop delivery back down inlet line - picture attached . I put a red hose on inlet side so I remember how to replumb it